Division of Botany, Indian Agricultural Research Institute, New Delhi
2Present address: Wheat Breeding Station, Powarkheda, Distt. Hoshangabad, Madhya Pradesh.
1Part of the thesis submitted by the senior author in partial fulfilment of the requirements of the degree of DOCTOR OF PHILOSOPHY of the Indian Agricultural Research Institute.
The objective of this investigation was to find out whether it is possible to screen a number of lines in a predominantly self-pollinated crop, like linseed, by adopting line x tester analysis and pick out those which may be of relatively greater potential value in the genetic improvement of yield. It was also desired to ascertain the degree of parallelism between ecogeographic divergence and genetic divergence and the adequacy of the tester in evaluating the lines.
The F1 of 54 crosses involving 3 testers and 18 lines and the F2 involving 1 tester and 17 lines (some of the latter being common in both the experiments) were grown and studied in 1960–61. All the parents were included in both the experiments. Observations were taken on 10 randomly chosen plants in the F1 and parents of Experiment 1 and on 20 plants in the F2 in Experiment 2. Data were recorded on flowering date, flowering duration, height of plants, maturity of capsules, number of capsules per plant, number of capsules per tiller, number of seeds in 10 capsules, 200-seed weight, and seed yield. Kempthorne's method of analysis of covariance of half-and full-sibs was used in the analysis of the data.
It appeared that for none of the ten characters was genetic variability predominantly additive. The nature of gene action could vary for the same character depending upon the cross.
Six lines, namely, T. 1193-2, N.P. (R.R.) 9, Safiligni, T. 477, S. 36, and I.P.I. 6, were found to possess high yield potentials and high g.c.a. effects for yield. The first three lines had high g.c.a. effects for a number of yield contributing characters also and hence were considered superior to others. The F2 data also confirmed the same. In screening of lines, more reliance was placed upon the general combining ability variances and their effects as these are expected to be stable over locations and seasons. Parental performance itself is not necessarily a guarantee of its usefulness in breeding programme.
Yield of seed, number of capsules per plant, flowering duration, and height of plants were found to be highly affected by environment.
A parallelism between ecogeographic diversity and genetic diversity was indicated in the present material.
The testers used were found to be qualitatively and quantitatively adequate as they themselves possessed high g.c.a. effects for yield and some of the yield components and as they evaluated the lines effectively.
Based on the results of this investigation, a procedure has been outlined for screening a wide range of germ plasm for utilizing the potentially useful lines in the programme for the genetic improvement of linseed.
